Marvin Miller — who as first executive director of the Major League Baseball Players Association had a greater impact on the national pastime than anyone since Jackie Robinson broke the color barrier in 1947 — according to some, it was a greater impact than anyone since Babe Ruth saved the sport in the 1920s after the Black Sox scandal — died Tuesday in New York. He was 95.

Miller died at his home in Manhattan at 5:30 a.m., said his daughter, Susan. He had been diag­nosed with liver cancer in August.

“Marvin Miller, I suspect, is the most effective union organizer since John L. Lewis,” writer Studs Terkel once said, referring to the longtime leader of the United Mine Workers.

When Mr. Miller joined the players association
in 1966, the average player salary was $19,000. By the time he retired, in 1982, it was $240,000. Players had gained the right to free agency and salary arbi­tration. And ownership’s ability to dominate the players was a thing of the past, a fact borne out by strikes in 1972 and 1981, the first in major league history, which were settled very much to the union’s advantage. (In 1972, Atlanta Braves general manager Paul Richards had fumed, “Tojo and Hirohito couldn’t stop baseball, but Marvin Miller could.”)

Those changes were all owing to the Major League Baseball Players Association. And as Mr. Miller’s successor Donald Fehr put it, “Marvin, for all intents and purposes, created the union.”

Mr. Miller’s success with the players association blazed a path for all professional athletes. The radical redressing of the imbalance between management and labor in baseball set an example for football, basketball, and hockey, a fact recognized by The Sporting News when it ranked Mr. Miller number five on its list of the 100 most influential people in sports in the 20th century.

“Marvin Miller has done so much for the players he can take a vacation for the next five years and he’ll still be ahead of us,” said Montreal Expos president John McHale in 1973. Los Angeles Dodgers owner Walter O’Malley put it more succinctly: “Marvin Miller is making us look like a bunch of idiots.”

Mr. Miller came to baseball from the United Steelworkers of America, where he had been associate director of research and then assistant to the president. “I loved baseball, and I loved a good fight, and, in my mind, ballplayers were among the most exploited workers in America,” he said.

So much of Mr. Miller’s success had to do with his ability to see baseball in a larger economic context, as a business as well as pastime. He never lost sight of the fact that players were also workers. This perspective gave him an enormous intellectual advantage over management, which rather than making relatively painless concessions on such issues as the reserve clause (which bound a player to the same team for his entire career) staked out unyielding positions that invariably proved untenable at the negotiating table, in the courts, or both.

Labor strife at the ballpark may have horrified owners and fans, but to Mr. Miller, with his background in foundries and mills, it seemed quite tame. “In any other industry — steel, auto, or coal — scholars would have remarked on the peaceful management-union relationship,” he wrote in his 1991 autobiography, “A Whole Different Ball Game: The Sport and Business of Baseball.”

Mr. Miller grew up a Brooklyn Dodgers fan and generally had a better command of baseball lore and statistics than any owner did.

Marvin Julius Miller was born in New York and grew up in Brooklyn. His mother, Gertrude (Wald) Miller, was a schoolteacher. His father, Alexander Miller, sold women’s clothing
and organized for the Retail, Wholesale, and Department Store Employees Union.

Mr. Miller attended Miami University, in Ohio, before transferring to New York University, where he majored in economics and graduated in 1938. After working for the Treasury Department and New York’s Department of Welfare, he served as an economist and disputes hearing officer for the US War Labor Board during World War II.

After the war, Mr. Miller took a position with the International Association of Machinists ­before joining the Steelworkers in 1950. He earned a growing reputation as a union negotiator, so much so that both Presidents Kennedy and Johnson appointed Mr. Miller to terms on the National Labor-­Management Panel.

After several years of being loosely organized, major league ballplayers had formed the Major League Baseball Players Association in 1965. Robin Roberts, a future Hall of Fame pitcher, then asked an economist he knew at the University of Pennsylvania to recommend a possible leader for the union. The economist named Mr. Miller. Initially, his candidacy was rejected by player representatives. But the full membership voted in Mr. Miller by a ratio of nearly 4 to 1 in 1966.

After his election, Mr. Miller was taken aside by Joe Cronin, the president of the American League. “I’ve got some advice for you,” he said. “The players come and go, but the owners stay forever.”

More prescient was the advice received by Bowie Kuhn, then assistant general counsel to the National League, when he asked a Harvard law professor how much help he would need now that the players had hired a union leader. The professor said, “Bowie, you need lots of help.”

Within two years, Mr. Miller had gotten the first across-the-board increase in the minimum salary in 20 years, from $6,000 a year to $10,000. Comparable improvements in travel, meal allow­ances, and pension benefits soon followed.

In 1970, the union backed Curt Flood, an outfielder who had been traded from St. Louis to Philadelphia, when he filed suit in federal court contending that the reserve clause was illegal. The Supreme Court dismissed the case two years later, but in so doing called the reserve clause an “aberration.”

The clause was overturned three years later. Encouraged by Mr. Miller, pitchers Andy Messersmith and Dave McNally filed a grievance after they had played a season without signing a contract and then had it automatically renewed. An arbitrator ruled in the players’ favor. A basic agreement negotiated by Mr. Miller and the owners in 1976 created the system of free agency that has remained in effect since then.

Mr. Miller retired from the union in 1982. A year later, he returned as executive director when his successor, Kenneth Moffett, was fired by the players. He stepped down in 1984, when Fehr was elected to the post.

In December 2002, Mr. Miller was nominated for inclusion in baseball’s Hall of Fame. He has not been elected for induction, however. “No man ever had the impact that that man had on the game,” former Red Sox general manager Lou Gorman once said. “Not Babe Ruth, not Ted Williams, not Sandy Koufax. No one.”

Besides his daughter, Mr Miller leaves a son, Peter, and a grandson.

Because of an editing error, an earlier version of this story said Miller died Friday. He died Tuesday.